Darkfire, I was looking at your blurry pic of the block and its clear(get it, pun, lol ohh I'm way too tired for this!!!) anyway, its clear that the top of cylinder flange has had some by-pass. See how dirty or discolored it is? that should be shiny!! You can tell the difference when the screws are tight against the head or screw shaft. If the Screw Shaft is bound, it fell feel springy, but if the head of the screw is tight against the cooling tight it will feel tight and firm!!! I realize its not a direct answer to your ?? but I feel it might be a better way to tell if the screw holes are threaded deep enough..

I do hope I made this clear enough and it helps.. Shees I'm tired,, no sleep for a couple days[&o]